Previous work has indicated that older and especially older obese rats are able to withstand prolonged starvation and conserve body protein. This adaptation appears to be due in part to a curtailment of skeletal muscle proteolysis. This adaptation to starvation appears to depend on the degree of adiposity of the rat and perhaps its age. To test this, a young rat will be made obese and starved to determine if it likewise conserves body protein during starvation when compared to its non-obese counterpart. Protein turn-over will be evaluated in the perfused rat hindquarter from the young obese rat model to determine if starvation is associated with a curtailment of muscle proteolysis. In addition, selected organs will be taken from young obese and non-obese rats to determine which organs loose protein and 3-methylhistidine early and which late in the fast. The ability to conserve body protein during starvation is dependent on the availability of lipid fuels. Studies to curtain their availability with either nicotinic acid or methyl-tetradecylglycidate will be performed in intact rats as well as in the perfused rat hindquarter and muscles incubated in vitro. Additional studies are planned to better define the relationship that exists between the exhaustion of lipid fuels during starvation and the enhancement of protein breakdown that it causes.